Recently, there has come known a method in which medical and diagnostic radiographic images are converted into a digital format that is picture-processed with a computer into a proper form for diagnoses, and then, reproduced into images on a light-sensitive material by exposure of laser beams.
In emergency medical area that strongly requires a rapid and correct diagnosis, rapid processing and high quality images are essential conditions of a light-sensitive material used.
This is the same with a silver halide photographic light-sensitive material for laser scanning. Therefore, it is necessary to develop a silver halide light-sensitive material having a much higher sensitivity and capable of providing images of much higher quality.
The present inventors proposed, in Japanese Patent Application No. 139607/1989, a method to improve sensitivity, gradation and graininess by optically sensitizing a specific silver halide emulsion with a specific carbocyanine.
By the way, in the manufacture of silver halide photographic light-sensitive material, coating emulsions are usually made to stand for several hours between the preparation thereof and the completion of coating. Therefore, stability of photographic characteristics for a long time is essential for a coating emulsion in use of mass production.
The above-mentioned method, however, had a disadvantage that a prolonged standing of a coating emulsion caused an increase in fog and a decrease in sensitivity, though the coating emulsion had satisfactory performance shortly after the preparation thereof.